1. Field of the Invention
The present invention relates to a system for informing a paper shift during a production controlling operation for an apparatus for producing corrugated paper boards.
2. Description of the Related Art
To facilitate understanding of the present invention, a typical conventional apparatus for producing corrugated paper boards will briefly be described below with reference to FIG. 4.
As shown in FIG. 4, the apparatus for producing corrugated paper boards is constructed such that webs 6 and 7 are conveyed from rolls mounted on a mill roll stand to a single facer 11 via splicers 20 and 21, the one web 7 is corrugated in the single facer 11 to form a core and the other web 6 is adhesively secured to the core thereby to produce a sheet of one-sided corrugated paper board 13 in the form of a continuous A flute. The one-sided corrugated paper board sheet 13 is conveyed to a double facer 16 via an overhead bridge 15, a three-staged preheater 26 and a gluing machine 33. In addition, another sheet of one-sided corrugated paper board 14 in the form of a B flute produced via the same steps as those for the one-sided corrugated paper board sheet 13 while having a different corrugation height as well as a web 10 in the form of a front liner paper are conveyed to the double facer 16 from rolls mounted on the mill roll stand via a splicer 24 and another three-staged preheater. The one-sided corrugated paper board sheets 13 and 14 and the front liner paper 10 are adhesively secured to each other in the double facer 16 thereby to produce a sheet of double-sided corrugated paper board 32. The double-sided corrugated paper board 32 is then subjected to slitting and scoring in an assembly 19 of slitter and scorer. Subsequently, it is cut to a predetermined length by actuating a rotary cutter 19.
Further, the apparatus performs a controlling operation for counting the number of sheets produced in the apparatus in the following manner. Specifically, the controlling operation is performed in such a manner as to calculate the position where a preset number of sheets can be produced with the present structure of each web and then execute a so-called lot shift (or a paper shift) at the foregoing position so as to allow to the present web to be spliced to a subsequent web having another structure. The lot shift is achieved in whole combination of the respective cores and webs. In other words, to carry out a lot shift, the present webs are spliced to subsequent webs of the kind corresponding to a next production lot in splicers 20, 21 and 24. With respect to not only a splice point for webs but also a splice point for cores which is directly measured with much difficulties, determination of splice points at which a web and a core are spliced to subsequent web and core has been hitherto accomplished by measuring a running length of each web-and then calculating a value representative of a running length of each core based on values derived from the measurements while the core running length value is added with a calculated take-up rate. As far as a sheet of corrugated paper board is concerned, the calculated take-up rate refers to a ratio of a length of each corrugated core in the extended state to a length of the liner paper, i.e., the web adhering to the core. When the calculated take-up rate is practically added with the value derived from the measurement of the running length of the web, the standard value which has been definitely predetermined corresponding to a height of the corrugated core is normally used.
Determination of splice points in the above-described manner is accompanied by many factors which may cause errors. One of such errors is caused when the liner paper and a final product of corrugated paper board are measured and a running length of the corrugated core is then determined based on the value derived from the measurement of the liner paper and the final product of corrugated paper board. Another error is caused when measurements are carried out with the aid of a rotary pulse signal generator and a slippage measuring instrument for measuring slippage between webs or sheets. Another error is caused when the liner paper and the final product of corrugated paper board expand or contract due to variation of a moisture content and a kind of paper to be measured. In addition, an error is caused when the final product of corrugated paper board is cut by actuating the rotary cutter 19. Finally, a sum of these errors appears in the form of an incorrect length as a result of superposition of the errors as mentioned above.
In recent years, many requests for a smaller lot in size (reduced number of corrugated paper boards) and reduction of a reject rate have been raised from users. The smaller the number of corrugated paper boards to be produced per one lot, the longer the erroneous part in a length of the final product of corrugated paper board. This causes the rate of rejection to be increased undesirably. In view of the aforementioned errors, the inventor has made proposals to reduce generation of errors as disclosed in two prior inventions, one of them being filed under Japanese Patent Application No. 114795/1989 with a title "A method of measuring a running sheet length in an apparatus for producing corrugated paper boards" and the other one being filed under Japanese Utility Model Application No. 61211/1989 with a title "An apparatus for controlling production and measurement in an apparatus for producing corrugated paper boards". The former prior invention is intended to prevent generation of measurement errors due to expansion and contraction of each web and obtain a measured value with higher accuracy on the running length measuring instrument side by properly correcting the measured value derived from the rotary pulse signal generator at a production speed of each web passing between mark sensors disposed with a predetermined distance therebetween. The latter prior invention is intended to prevent generation of errors due to expansion and contraction of each web by measuring a running length of each of webs for a liner paper and a corrugated core, calculating a splice point for each of the webs to be spliced to each other based on a value derived from the measurement and then adding the value derived from the measurement of a running length of each web with a calculated take-up rate in a case where a value derived from measurement of liner paper including an error value unchangeably is used in place of a running length of the corrugated core.
Since the controlling operation for the apparatus for producing corrugated paper boards is performed based on a production length of each final product of corrugated paper board, and moreover a constant value controlling process utilizing a manual speed command or a standard speed command depending on conditions such as a kind of paper or the like is employed for the purpose of determining a production speed, there does not arise any particular problem in a case where a lot size is large in length and a production length of each final product of corrugated paper board is longer than a line stay length between the rotary cutter 19 and the splicers 20, 21 and 24. In recent years, however, since many requests for a smaller lot size have been raised from users, there may arise an occasion that a paper shifting operation to be performed in response to an order change for webs to be subsequently spliced cannot follow the present production speed. In other words, a paper shifting operation has been hitherto manually performed by an operator under a condition that a time required for performing a splicing operation is recognized as a standard time. In addition, an operational setting time having the standard time added with some allowance time is assured so as not to cause a malfunction during a normal operation of the apparatus. However, in a case where an order is given with a small lot in length shorter than the operational setting time, there may arise a trouble when a paper shifting operation is performed. In addition, since the time when an operator performs a paper shifting operation is determined at his own discretion depending on a quantity (length) of unfeeling of a web from the mill roll stand, other problems are that a highly trained skill is required for accomplishing the paper shifting operation and the operator erroneously determines the time when the paper shifting operation is properly performed.